Non-perturbative chiral approach to s-wave (K)over-barN interactions

The s-wave meson-nucleon interaction in the S=−1 sector is studied by means of coupled-channel Lippmann Schwinger equations, using the lowest order chiral Lagrangian and a cut off to regularize the loop integrals. The method reproduces succesfully the Λ(1405) resonance and the K−p→K−p,K¯0n,π0Λ,π0Σ,π+Σ−,π−Σ+ cross sections at low energies. The inclusion of the ηΛ,ηΣ0 channels in the coupled system is found very important and allows a solution in terms of only the lowest order Lagrangian.